^start of line
\s*a Unicode whitespace character, repeated any number of times
\w+a Unicode word character, repeated at least once
Non-Capturing Group(?: \d{2}){3} {3}repeats the group contents below exactly 3 times:
the literal (3210 / 408 / 2016)
\d{2}a Unicode decimal digit, repeated exactly 2 times
\s*a Unicode whitespace character, repeated any number of times
g modifier: global. Finds all matches instead of stopping after the first
m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string